iPP/PE Multiblock Copolymers for Plastic Blend Recycling Synthesized by Coordinative Chain Transfer Polymerization

Abstract

Recycling of blends of widely used plastics is a key challenge of the envisioned circular economy, and thus, protocols permitting the efficient synthesis of effective compatibilizers are highly desirable. We report herein that coordinative chain transfer polymerization permits the efficient one-pot synthesis of multiblock architectures of strictly linear polyethylene or high-density polyethylene (HDPE) and isotactic polypropylene (iPP). Various block copolymers having an iPP backbone and HDPE side chains were synthesized and used to compatibilize HDPE/iPP plastic blends. The synthesized block copolymers differ in their overall molecular weights and have different HDPE side chain lengths and numbers. A block copolymer with a molecular weight of M p = 33,700 g × mol −1 including 4.5 HDPE side chains with a molecular weight of M n = 600 g × mol −1 showed the highest efficiency for compatibilizing 30/70 wt % blends of HDPE/iPP with a 5 wt % compatibilizer addition. This block copolymer is also superior to commercially available compatibilizers.

Adhesion to Untreated Polyethylene and Polypropylene by Needle-like Polyolefin Crystals

“…Charge was neutralized using a 1 keV electron beam. Negative secondary ions corresponding to 1 H, 12 C, 12 C 1 H 1 H, 12 C 14 N, 28 Si, and 35 Cl were monitored as functions of time. The positions of the true surface and substrate interface were determined on the basis of the 35 Cl and 28 Si ion profiles, respectively.…”

“…Negative secondary ions corresponding to 1 H, 12 C, 12 C 1 H 1 H, 12 C 14 N, 28 Si, and 35 Cl were monitored as functions of time. The positions of the true surface and substrate interface were determined on the basis of the 35 Cl and 28 Si ion profiles, respectively. The sputtering time was converted into depth from the air surface based on thickness determined by ellipsometry, assuming a steady sputtering rate.…”

“…On the other hand, polyolefins are poorly adhesive; this lack of adhesive strength and resultant interfacial mechanical weakness pose serious challenges for their recycling in commingled plastic waste. − As a result, this plastic waste has polluted the environment through landfills and ocean outflows. , Although adhesive strength can be improved by functionalizing the polyolefin surface with polar groups or by forming covalent bonds across interfaces, − these approaches are hardly applied to plastic waste owing to a lack of economic incentive. − Adhesive strength can also be increased by welding together polymer–polymer contacts using compatibilizers, such as block copolymers. − However, a compatibilizer must be customized for each pair of polymers, which presents recycling difficulties due to wide variations in commingled plastic waste pairings. To avoid these practical issues, current recycling methods are required to sort commingled plastic waste, resulting in a recycling rate of only 9% in the USA .…”

Coordinative Chain Transfer Polymerization of Butadiene Using Nickel(II) Allyl Systems: A Straightforward Route to Branched Polybutadiene

“…8 If CCTP studies using nickel ). 15,17,18 Branched polymers are of high interest as they offer a range of advantages over their linear counterpart. In particular, the branched structure provides lower crystallinity, thus improving elasticity and toughness, and a lower viscosity, which enhances processability.…”

Structures of the co‐branching reactive products of isotactic polypropylene with high‐density polyethylene and the effect on the in situ compatibilization of mixed recycled materials

“…Currently, due to their excellent compatibilization effects, the preparation of controllable long chain segment copolymers and their structure-property relationships are becoming a hot research topic in regards to the high-quality recycling of polyolefin mixed waste plastics. 16,[24][25][26][27][28][29] In our previous study, 30 trimethylolpropane triacrylate (TMPTA), 2,5-dimethyl-92,5-di(tert-butylperoxy) hexane (DHBP), and zinc dimethyldithiocarbamate (ZDMC) were used to economically and conveniently generate the long chain co-branched copolymers in situ for compatibilization of HDPE and IPP blends. Consequently, superior compatibility and mechanical properties of the HDPE/PP blends were obtained.…”